You can avoid a penalty by filing and paying your tax by the due date. If you can't do so, you can apply for an extension of time to file or a payment plan.
You may face tax late filing and/or late tax payment penalties if you file after the deadline and owe taxes.
The Failure to File Penalty is 5% of the unpaid taxes for each month or part of a month that a tax return is late.
The penalty won't exceed 25% of your unpaid taxes
If you file more than 60 days late, your minimum failure-to-file penalty will be 100% of your unpaid taxes or $435 (whichever is less)
If you do not pay the full amount you owe by the tax deadline, even if you file an extension, you will be assessed a penalty of 0.5% of your balance due per month or part of a month after the deadline.
If you do not pay your full balance due, you will also owe interest on the unpaid amount.
The interest rate is set quarterly by the federal government. The current 2021 interest rate for underpayment of taxes is 3%.